1. Field of the Invention
The present invention relates to a compact and powerful rotary electric machine to be used for a passenger car, an airplane and an electric power tool.
2. Description of the Related Art
A typical rotary electric machine to be used for a vehicle is an alternator that has a Lundell type rotary magnetic core. The Lundell type rotary magnetic core is composed of a boss portion, a pair of disk portions disposed at opposite ends of the boss portion and a plurality of claw poles extending from the disk portions in the axial direction of the core to alternately interleave with each other. A cylindrical field coil is wound around the boss portion to supply magnetic flux to parallel magnetic circuits that respectively include the claw poles. Therefore, comparatively large magnetomotive force can be applied to the claw poles, so that the alternator can generate comparatively high power.
However, the thickness of the claw poles have to be limited in order to limit the outside diameter of the alternator. This limitation may cause DC magnetic saturation, which limits an amount of effective magnetic flux and output power of the alternator.
In order to increase the effective magnetic flux, it has been proposed that a permanent magnet is inserted between adjacent claw poles. However, the space for accommodating the permanent magnets is limited and cooling performance of the alternator may get worse because the permanent magnets close air passages.